Frame for stressing sheet material



De.9, 1969 K.J.HAMU 3,482,343

FRAME FOR STRESYSING SHEET MATERIAL Filed Jan. 22, 1968 2 Sheets-Sheet l1 f [Ol F11 im e 1 e I l y. e e

52: .m1/ENTOR- 50/V 50 5-4/ 34 Km2/g 4A HAMU /4 Trae/vm Dec. 9, 1969 K.J. HAMU 3,482,343

FRAME FOR sTREssING SHEET MATERIAL 2 Sheets-Sheet 2 Filed Jan. 22,l 1968za. l0.

' M @am 300 2/4 A 7mm/EY United States Patent O 3,482 343 FRAME FORSTRESSIG SHEET MATERIAL Kaino J. Hamu, 2663 Chico St., El Monte, Calif.91733 Continuation-impart of application Ser. No. 633,261, Apr. 24,1967. This application Jan. 22, 1968, Ser. No.

Int. Cl. D06c 3/08 U.S. Cl. 38-102.5 6 Claims ABSTRACT F THE DISCLOSUREA stretch frame for biaxially stressing sheet material, such as printingscreen, in mutually perpendicular edgewise directions, the frame havingframe members mounting floating bars for attachment to the edges of thesheet material to be stressed, and means independently adjusting theframe members and oating bars to stress the sheet material in theedgewise direction in such a Way as to permit both coarse and tineadjustments of the sheet tension.

This application is a continuation-in-part of my copending applicationSer. No. 633,261, filed Apr. 24, 1967, and entitled Frame for StressingSheet Material.

BACKGROUND OF THE INVENTION Field of the invention A variety of stretchframes or screen chases of the character described have been devised.These exlsting frames, however, are characterized by excessivecomlpleXity and cost of manufacture, lack of both coarse and linetension adjustments, difficulty of use, and other undesirable features.

SUMMARY OF THE INVENTION The primary object of this invention is toprovide an improved stretch frame of the character described which isnot subject to the above noted and other deficiencies.

A more specific object of the invention is to provide an improvedstretch frame of the character described lwhich is characterized bysimplicity of construction,

economy of manufacture, capability of both coarse and tine adjustment ofthe tension in the sheet material being stressed, ease of use, and otherhighly desirable and benecial features.

A further object of the invention is to provide a stretch frame of thecharacter described which is uniquely adapted for use as a screen chasein the silk screen printing in- Y dustry.

Other objects, advantages, and features of the invention will becomereadily evident as the description proceeds.

With these and such other objects in veiw, the invenvtion consists inthe construction, arrangement, and combination of the various parts ofthe invention, whereby the objects contemplated are attained, ashereinafter set forth, pointed out in the appended claims, andillustrated in the accompanying drawings.

lCC

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a plan view of a stretchframe, or screen chase, according to the invention;

FIGURE 2 is an edge View of the frame in FIGURE 1 with parts broken awayfor the sake of clarity;

FIGURE 3 is an enlarged fragmentary section through one corner of theframe;

FIGURE 4 is an enlarged section taken on line 4-4 in FIGURE 2;

FIGURE 5 is an enlargement of the area enclosed by the circular arrow 55 in FIGURE 4;

FIGURE 6 is an enlarged fragmentary section through a modified stretchframe or screen chase according to the invention;

FIGURE 7 is a perspective view of a further modified stretch frame orscreen chase according to the invention;

FIGURE 8 is an enlarged section taken on line 8-8 in FIGURE 7;

8 FIGURE 9 is an enlargement of a portion of FIGURE gand FIGURE 10 is afragmentary enlargement of a further modied stretch frame or screenchase according to the invention.

In general terms, the invention provides a stretch frame, or screenchase, represented in the drawings by the frame 10, having a pair ofspaced and generally parallel rst side frame members 12, a pair ofspaced and generally parallel second side frame members 14 extendingnormal to the lirst members, and corner means 16 joining the adjacentend-s of the frame members for relative adjustment of the frame members12 along a direction line 18 parallel to the frame members 14 andrelative adjustment of the frame members 14 along a direction line 20parallel to the frame members 12. Thus, the frame members are relativelyadjustable to vary the spacing between the parallel frame members 12 andthe spacing between the parallel members 14. Also embodied in thestretch frame is a set of floating bars for attachment to the edges ofthe sheet material to be stressed. This set of floating bars includes apair of first bars 22 adjacent and parallel to the frame members 12,respectively, and a pair of second bars 24 adjacent and parallel to theframe members 14, respectively. The floating bars 22, 24 are mounted onthe respective frame members 12, 14 by mounting means 26 which areadjustable to adjust the bars relative to the frame members. Thus, thebars 22 are adjustable relative to their respective adjacent framemembers 12 along the direction line 18. The bars 24 are adjustablerelative to the frame members 14 along the direction line 20. Thefloating bars 22, 24 are equipped with means 28 for securing the bars tothe sheet material 30 to be stressed. l

Briefly, in use of the stretch frame or screen chase 10, the framemembers 12, 14 and the floating bars 22, 24 are adjusted inwardlyto'eiectively contract the frame suciently to enable a sheet material 30to be laid across the frame with the marginal edges of the materialoverlying the floating bars. The sheet material is then attached to thebars by securing means 28. Thereafter, the frame members and the oatingbars are adjusted outwardly to biaxially stress the sheet material inedgewise directions parallel to the direction lines 18, 20. In thisregard, a feature of the invention resides in the fact that adjustmentof the frame members 12, 14 provides a coarse tension adjustment, theadjustment of the floating bars 22, 24, provides a line tensionadjustment for the sheet material.

Referring now in greater detail to the illustrated stretch frame orscreen chase 10, the frame members 12 and 14 will be observed tocomprise tubes of rectangular cross section. While the frame members maybe of equal length in some cases, the frame members 14 of theillustrated frame are shown to be somewhat longer than the frame members12. The corner means 16 of the frame comprise generally L-shaped cornermembers 32 which are preferably castings. Each corner member has a pairof mutually perpendicular arms 34 which fit slidably within and haveframe tubes 12, 14. The juncture of the arms 34 of each corner member isenlarged slightly relative to the arms to form a cube-like cornerportion 36. This corner portion defines shoulders 38 facing andengageable with the adjacent frame tubes to limit relative telescopingmovement of the tubes and corner members.

In addition to the corner members 32, each corner means 16 of theillustrated frame comprise a pair of socket adjusting screws 40, 42which extend through longitudinal bores 44 in the arms 34 of thecorresponding corner member 32. The screw heads are accessible throughopenings 46 in the corner portions 36 of the corner members to permitengagement of the screw heads with a wrench, or the like, for rotatingthe screws. The threaded shanks of the screws extend beyond the arms 34of the corner members, as shown, and mount fixed thrust shoulders 48which engage in sockets in the end faces of the arms, as shown. In thepresent instance, these thrust shoulders comprise nuts which are weldedor otherwise rigidly fastened to the screws. Fixed within the ends ofeach frame tube 12, 14 are nuts 50 having threaded bores 52 axiallyaligned with and threadedly receiving the threaded shanks of theadjacent adjusting screws 42. The illustrated nuts comprise metal blockswhich complement the interior of the frame tubes and are fixed in placeby dimples 54 in the tubes which protrude into recesses in the blocks.

It is evident at this point that adjustment of the screws 40 iseffective to relatively adjust the frame members or tubes 12 along thedirection line 18, thus to vary the spacing between these members.Adjustment of the screws 42 is effective to relatively adjust the framemembers or tubes 14 along the direction line 20` to vary the spacingbetween these members. Thus, the frame can be expanded and contracted byrotation of the corner adjusting screws. Of notable significance is thefact that the adjusting screws are effective to both positively contractand positively expand the frame; that is to say, rotation of the screwsin one direction is effective to positively separate the frame membersand thereby expand the frame. Rotation of the screws in the oppositedirection is effective to positively move the frame members toward oneanother and thereby contract the frame.

The floating bars 22, 24 which support the sheet material 30 compriselong slender bars of rectangular cross section. As shown best in FIGURE4, the floating bars are disposed with corresponding sur-faces thereoffacing and located substantially flush with the normally upper sides ofthe frame members 12, 14. Extending between the frame members and theirrespective adjacent floating bars are adjusting screws 56 whichconstitute the floating bar mounting means 26. Adjusting screws 56 arerotatable in their respective frame members and have their heads exposedat the outer sides of these members to permit the screws to be turned.The threaded shanks of the adjusting screws project inwardly a distancebeyond the frame members and are threaded in the adjacent floating bars.As shown in FIGURE 3, these adjusting screws 56 are retained againstmovement relative to the respective frame members by the screw heads andby flanges 57 formed as by welding washers to the screw Shanks, in orderto provide for positive selective movement by the screw of the bars ineither direction. Thus the floating bars 22, 24 are positivelyadjustable both inwardly and outwardly along the direction line 18,relative to the frame members 12, 14 and independently of adjustment ofthese frame members. Referring to FIG. 4, it will be observed that theadjusting screws 40, 42, and 56 are offset so as to not interfere withone another.

As noted earlier, the floating bars 22, 24 have means 28 for attachingthe bars to the marginal edges of the sheet material 30 to be stressed.These attaching means comprise longitudinal solts or grooves 58 whichenter the normally upper surfaces of the bars. Each groove is undercutto define a shoulder 60 along the open side of the groove. Removablypositioned within each groove is an anchor strip 62 which is laterallydimensioned to lit diagonally in the groove, in the manner illustratedin FIG- URE 4.

In use, the stretch frame or screen chase 10 is initially contracted, byinward adjustment of the frame members 12, 14, sufliciently to enablethe sheet material 30 to be llaid over the frame with the marginal edgesof the material overlying the floating bars 22, 24. The sheet materialis then secured to these bars by pressing the edges of the material intothe bar grooves 58 and then inserting the anchor strips 62 into thegrooves, over the sheet material, so that the strips engage under thebar shoulder 60, as shown in FIGURE 5, thus to firmly anchor thematerial to the bars.

At this point, the outer frame adjusting screws 40, 42 are rotated indirections to separate the opposing frame members 12, 14 and therebyinitially tension or stress the sheet material 30 in edgewise directionsparallel to the direction of lines 18, 20. This adjustment, in effectprovides a coarse tension adjustment for the sheet material. Thereafter,the floating bar adjusting screws 56 are rotated to finally tension orstress the sheet material. This latter adjustment provides a finetension adjustment for the sheet material. With regard to this finetension adjustment, it is evident that the floating bar adjusting screws56 may be independently adjusted to equalize, with a high degree ofaccuracy, the tension in all portions of the material 30 and in theedgewise directions of both direction lines 18 and 20.

Lateral insertion of the anchor strips 62 into the floating bar grooves58 is desirable for the reason that it greatly facilitates attachment ofthe sheet material to the floating bars 22, 24. Obviously, the anchorstrips may be removed laterally from the grooves to release, with equalfacility, the sheet material from the floating bars. As noted earlier,the present stretch frame may be utilized for a variety of purposes butis intended primarily as a screen chase in the silk screen printingindustry for supporting silk printing screens, or the like, in a tautcondition. Obviously, the frame may be also utilized to support fabric,wire mesh, and a variety of other sheet-like materials.

Turning now to FIGURE 6, there is illustrated a modified stretch frameaccording to the invention which is identical to the stretch frame justdescribed except for the floating screen anchor bars 102 which are usedin the modified frame. In this case, each floating bar has a flange 104extending from the side of the bar opposite its screen receiving groove106. Also, the adjacent ends of the four floating bars of the stretchframe are bridged by fluid seals 110. In this instance, the fluid sealscomprise strips of tape which are secured to the inner surfaces of thefloating bars, as shown. The modified stretch frame 100 is placed in itsinverted sloping position shown when applying ink to the frame screen112, In this position, thc floating bars 102 and their currentlyupstanding flanges 104, and the seals between the adjacent floatingbars, provide a well for retaining ink on the screen.

FIGURES 7 through 9 illustrate a further modified screen frame 200according to the invention. In this case, the outer frame members 202,204 are rigidly joined by welding their adjacent ends to one another. Aswill be explained presently in connection with FIGURE l0, however, thesemembers may be adjustably joined in much the same way as the framemembers of the earlier described stretch frames. Also, the frame members202, 204 have modified cross sections which may be best observed inFIGURE 9. Referring to this latter figure, it will be seen that eachframe member is essentially a hollow rectangular tube with upstandingflanges 206 along its opposite longitudinal sides. Flanges 206 definetherebetween an upwardly opening channel 208. Channels 208 contain theoating screen anchor bars 210, 212 of the modified stretch frame. Eachfloating bar is supported on its respective frame member 202, 204 by anumber of adjustable lead screws 214. Each lead screw extends betweenand is journalled at its ends in the fianges 206 of the respective framemember. The lead screws are axially restrained by the illustratedshoulder means, whereby the screws are free to rotate, but are securedagainst axial movement. Each oating bar 210, 212 has threaded boresthrough which its respective lead screws 214 pass. Accordingly, rotationof the lead screws for each oating bar is effective to laterally adjustthe bar relative to its adjacent frame member 202, 204.

The oating bars 210, 212 are essentially identical to the floatingscreen anchor bars of the first described embodiment of the inventeion.Thus, the sole difference between the oating bars resides in the factthat the oating bars 210, 212 of FIGURES 7 through 9 have screws 216 forlocking their screen anchor strips 218 in clamping engagement with theframe screen 220. In this regard, it will be observed that the groovedsides of the floating bars are exposed at the open sides of the framechannels 208 and are substantially flush with the yupper edges of theframe flanges 206.

The modified stretch frame 200 is used in essentially the same Way asthe first described stretch frame of the invention. The modified stretchframe, however, permits inward adjustment of the floating bars 210, 212,to create slack in the screen 220 during washing of the screen, withoutinadvertent release of the screen from the coating bars.

As noted earlier, the outer frame members 202, 204 of the stretch framejust described may be adjustably joined in the manner illustrated inFIGURE 10, rather than Welded, as sho'wn in FIGURE 7. In this case, theframe members are joined by corner members 300 which are essentiallyidentical to the corner members in the first described stretch frame ofthe invention and are inserted into the open ends of the lo'wer tubularportions of the frame members. The corner members and frame members arejoined in the same manner as in the first described stretch frame,whereby the frame members may be adjusted relative to one another, asbefore.

Clearly, therefore, the invention herein described and illustrated isfully capable of attaining the several objects and advantagespreliminarily set forth.

The inventor claims:

1. A frame for biaxially stressing sheet material in mutuallyperpendicular edgewise directions comprising:

an open rectangular frame having a central opening bounded by side andend frame members,

a pair of first floating bars adjacent and parallel to said side framemembers,

a pair of second floating bars adjacent and parallel to said end framemembers,

adjustable mounting means supporting said bars on their respectiveadjacent frame members for adjustment of said first bars lengthwise ofsaid frame and adjustment of said second bars laterally of said frame,

said bars including means for attaching the marginal edges of said sheetmaterial to said bars, and seal means joining the adjacent ends of saidbars S0 as to define with said sheet material a well.

2. A stretch frame according to claim 1 wherein:

said floating bars include upstanding anges for increasing the depth ofsaid well, and

said seal means comprise tape secured to the inner surfaces of theadjacent bars.

3. A frame for biaxially stressing sheet material in mutuallyperpendicular edgewise directions comprising: an open rectangular frameincluding side and end frame members,

a pair of rst fioating bars adjacent and parallel to said side framemembers,

a pair of second floating bars adjacent and parallel to said end framemembers,

adjustable supporting means supporting said bars on their respectiveadjacent frame members for adjustment of said first bars laterally ofsaid frame and adjustment of said second bars longitudinally of saidframe, and

said bars having normally upwardly opening grooves to receive themarginal edges of said sheet material, angularly disposed anchor stripspositioned in said grooves for gripping said marginal edges, and screwscarried by said bars and engageable with said anchor strips forretaining the latter in gripping engagement with said marginal edges.

4. A frame for biaxially stressing sheet material in mutuallyperpendicular edgewise directions comprising: an open rectangular framehaving a central opening bounded by side and end frame members,

each said frame member having a normally lower tubular portion andupstanding flanges defining therebetween an upwardly opening channel,

a pair of first fioating bars positioned within and extendinglongitudinally of the channels in said side frame members,

a pair of second iloating bars positioned within and extendinglongitudinally of the channels in said end frame members,

lead screws journalled at their ends in the flanges of each frame memberand passing through threaded bores in the corresponding floating bar,whereby rotation of said lead screws is effective to adjust said rstfloating bars laterally of said'frame and said fioating barslongitudinally of said frame, and

means for attaching the marginal edges of said sheet material to saidbars.

5. A stretch frame according to claim 4 wherein:

the adjacent ends of said frame members are rigidly joined as bywelding.

6. A stretch frame according to claim 4 wherein:

said frame members are relatively adjustable and have adjacent openends, and

adjustable corner means extending into and adjustably joining theadjacent ends of said frame members.

References Cited UNITED STATES PATENTS 1,223,015 4/1917 Woodley 38-l02.51,895,309 l/l933 Boomershine 38-l02.91 2,803,086 8/1957 Ross E18-102.12,893,162 7/1959 Knowles 3\8-102.1 3,255,540 6/1966y Gilman S55-102.913,359,663 12/1967 Black 38-102.9l

FOREIGN PATENTS 126,170 6/ 1928 Switzerland.

PATRICK D. LAWSON, Primary Examiner U.S. Cl. X.R. 38--l02.91

UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3 ,482,343 December 9 l969 Kaino J. Hamu It is certified that error appears inthe above identified patent and that said Letters Patent are herebycorrected as shown below:

Column 6 after line 52 insert the following claims 7 A frame forbiaxially stressing sheet material in mutuall'I perpendicular edgewisedirections comprising:

a pair of spaced and generally parallel first frame members a pair ofspaced and generally parallel second frame members extending betweencorresponding ends of and generally normal to said first frame memberscorner members at the corners respectively, of said frame and disposedin slidable telescoping engagement with the adjacent fra:

members whereby said corner members join the adjacent ends of said framemembers for relative adjustment of said first frame members along firstdirection lines paralled to said second frame members to vary thespacing between said first frame member and relative adjustment of saidsecond frame members along second direction lines paralled to said firstframe members to vary the spacing between said second frame membersadjusting means connected between said corner members and theirrespective adjacent frame members for independently relatively adjustingeach corner member and each of its adjacent frame members in the endwisedirection of the frame members said adjusting means comprising a pair ofrotatable axially fixed adjusting screws carried by each corner memberwith the screw axes extending longitudinally of the adjacent framemembers respectively, and nuts threaded on said adjusting screws andfixed within the respective adjacent frame members a pair of firstfloating bars adjacent and extending longitudinal of said first framemembers respectively,

a pair of second floating bars adjacent and extending longitudina ofsaid second frame members respectively,

adjustable mounting means supporting said bars on the respectiveadjacent frame members for adjustment of said first bars relative tosaid first frame members along said first direction line and adjustmentof said second bars relative to said second frame members along saidsecond direction line,

said floating bars including means for attaching to said bars themarginal edges of a sheet to be stressed, and

said frame members and floating bars being independently adjustable tobiaxially stress said sheet in edgewise directions parallel to saiddirection lines.

8r A stretch frame according to Claim 7 wherein: said frame memberscomprise tubes of rectangular cross section, and said corner memberscomprise mutually perpendicular arms slidably disposed within and havingrectangular cross sections complementing the central openings in saidtubes.

9. A frame for biaxially stressing sheet material in mutuallyperpendicular edgewise directions, comprising: a pair of spaced andgenerally parallel first frame members comprising tubes of rectangularcross-section, a pair of spaced and generally parallel second framemembers extending between corresponding ends of and generally normal tosaid first frame members, said second frame members comprising tubes ofrectangular cross-section, corner means joining the adjacent ends ofsaid frame members for relative adjustment of said first frame membersalong first direction lines parallel to said second frame members tovary the spacing between said first frame members, and relativeadjustment of said second frame members along second direction linesparallel to said first frame members to vary the spacing between saidsecond frame members, said corner means comprising generally L-shapedcorner members having mutually perpendicular arms slidably disposedwithin and having rectangular cross-sections complementing the centralopenings in their respective tubular frame members, a pair of firstfloating bars adjacent and extending longitudinally of said first framemembers, respectively, a pair of second floating bars adjacent andextending longitudinally of said second frame members, respectively,adjustable mounting means supporting said bars on the respective framemembers for adjustment of said first bars relative to said first framemembers along said first direction line and adjustment of said secondbars relative to said second frame members along said second directionline, said floating bars including means for attaching to said bars themarginal edges of a sheet to be stressed, and said frame members andfloating bars being independently adjustable to biaxially stress saidsheet in edgewise directions parallel to said direction lines.

l0. A frame for biaxially stressing sheet material in mutuallyperpendicular edgewise directions comprising a pair of spaced andgenerally parallel :first frame members,

a pair of spaced and generally parallel second frame members extendingbetween corresponding ends of and generally normal to said first framemembers,

corner means joining the adjacent ends of said frame members forrelative adjustment of said first frame members along first directionlines parallel to said second frame members to vary the spacing betweensaid first frame members and relative adjustment of said second framemembers along second direction lines parallel to said first frame"members to vary the spacing between said second frame membedrs a pairof first floating bars a jacent and extending longitudinally of saidfirst frame members, respectively, a pair of second floating barsadjacent and extending longitudinally of said second frame members,respectively, adjustable mounting means supporting said bars on theirrespective adjacent frame members for adjustment of said first barsrelative to said first frame members along said first direction line andadjustment of said second bars relative to said second frame membersalong said second direction line,

said floating bars having corresponding surfaces and substantially flushwith the normally upper surfaces of said frame members, undercutlongitudinally extending grooves entering said surfaces of said floatingbar's and defining shoulders along the open sides of the respectivegrooves, and anchor strips laterally insertable into said groovesthrough said open sides thereof and engageable under said shoulders forattaching to said floating bars the marginal edges of a sheet to bestressed, and

said frame members and floating bars being independently adjustable tobiaxially stress said sheet in edgewise direction parallel to saiddirection lines.

ll, A stretch frame according to Claim l0 wherein: said frame membersdefine a central rectangular opening in said frame, and said bars aredisposed within said opening along the inner sides of the respectiveframe members.

l2 o A frame for biaxially stressing sheet material' in mutuallyperpendicular edgewise directions, comprising:

a pair of spaced and generally parallel tubular first frame members,

a pair of spaced and generally parallel second tubular frame membersextending between corresponding ends of and generally normal to saidfirst frame members,

generally L-shaped corner members at the corners respectively, of saidframe and each including generally mutually perpendicular arms slidablyfitted within the ends of the respective adjacent frame members firstadjusting screws extending between said corner members and said firstframe members lengthwise of said first frame members and operativelyconnected between said corner members and said first frame memberswhereby rotation of said screws effects relative adjustment of saidcorner members and said first frame members lengthwise of said firstframe members second adjusting screws extending between said cornermembers and said second frame members lengthwise of said second framemembers and operatively connected between said corner members and saidsecond frame members whereby rotation of said second adjusting screwseffects relative adjustment of said corner members and said second framemembers lengthwise of said second frame members said adjusting screwsbeing adjustable to effect relative adjustment of said first framemembers along first direction lines parallel to said second framemembers to vary the spacing between said first frame members andrelative adjustment of said second frame members along second directionlines parallel to said first frame members to vary the spacing betweensaid second frame members and means for attaching to said frame membersthe marginal edges of a sheet to be stretched.

13. A stretch frame according to Claim l2 wherein: said sheet attachingmeans comprise means on said frame members having undercut groovesextending longitudinally of said frame members, respectively, andopening through one side of said frame said grooves defining shouldersalong the open sides of the respective grooves and anchor stripslaterally insertable into said grooves through said open sides thereofand engageable under said shouldersU In the heading to the printedspecification, line 8 "6 Claims." Should read 13 ClaimsQ Signed andsealed this 10th day of November 1970 (SEAL) Attest:

EDWARD M.FLETCHER,JRe WILLIAM E. SCHUYLER, JI Attesting OfficerCommissioner of Patents

